Seiko 7A38 - by the numbers

Forums

Post Reply
Forum Home > Bend it, Mend it - Mods & Wreckers > 7A28-7049 - NOS, but nothing is working at all... :(

MTX371
Member
Posts: 46

Hi guys,

I have a 7A28-7049 in NOS condition.
Got it with a broken stem, put a new one in and it fits very well.
After inserting a Maxell 394 nothing happened. Nothing.
Tried it with heat and "kicking" the second hand - again nothing.
Movement and everything looks like new.

How can I go on?

Best regards


May 28, 2014 at 3:28 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8885

Tim.

Have you checked the height of the setting lever; making sure it is still making contact with the PCB ? (I think we've been here before).


See: http://www.seiko7a38.com/apps/forums/topics/show/12096528-7a28-702a-chronograph-setting-problem

and: http://www.seiko7a38.com/apps/forums/topics/show/9397929-problems-with-stem-and-resetting-chrono-hands


Another thought. You say: but nothing is working at all... :(

Do you mean no time; no chronograph functions and no self-test ?

If that is the case, have you tried swapping the PCB for a known good one ?


May 28, 2014 at 7:36 AM Flag Quote & Reply

MTX371
Member
Posts: 46

Hi Paul,

NOTHING works... Not time, no stopwatch, no self-test. No manual adjustment of the hands. No "ticking". The only thing working is of course adjusting time and day / date manually.

Don´t have a "single" PCB... :( Few time at the moment for picking out a one from a working watch...

Will try to have a look at the PCB the next days. The watch looks like from the dealer - can´t imagine that there should be a fault in the PCB.


May 29, 2014 at 3:47 PM Flag Quote & Reply

donwatch
Member
Posts: 504

Tim, try taking the back plate off and re-installing and then testing with battery before you tear down another watch. :/ Just a quick thought :P

May 29, 2014 at 4:01 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8885

Well in the absence of a 'spare' known good PCB, I'll re-iterate my initial response:


Have you checked the height of the setting lever; making sure it is still making contact with the PCB ? (I think we've been here before).


Whoever broke the crown stem may have bent the setting lever linkage. :/


May 30, 2014 at 9:42 AM Flag Quote & Reply

MTX371
Member
Posts: 46

Guys... That watch couldn´t work at all!



 

Is the PCB still available @ Cousins? Or anywhere else?


May 30, 2014 at 3:50 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8885

The good news is that the setting lever appears to have been set at the correct height, Tim ! :P

May 30, 2014 at 3:54 PM Flag Quote & Reply

7ARCool
Member
Posts: 168

HaHaHa.  :lol:

I have a battered 7a28-7040/9 in need of a new case/bracelet................... :roll:

SEIKO 7A28-7040 photo IMAG0156.jpg

May 30, 2014 at 4:08 PM Flag Quote & Reply

Sir Alan
Member
Posts: 451

I can see the problem - the finger spring is slightly off centre. An easy fix ;)

May 30, 2014 at 4:19 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8885

Is the PCB still available @Cousins? Or anywhere else?


Looks like you're going to need one of these, Tim. Luckily for you, although Seiko list them as obsolete, Cousins still have some stock.


http://www.cousinsuk.com/search-results?searchtext=4001725



PS - May I politely suggest, Tim, that next time, before you waste our time, trying to diagnose your 'totally dead' symptoms for you ....

that you first undo the 7 back-plate screws and eliminate the bleedin' obvious. :roll:


May 30, 2014 at 4:49 PM Flag Quote & Reply

MTX371
Member
Posts: 46

Aaaaah... I am wasting your time? I understand... I beg your pardon.

Am I still allowed to ask questions or is that prohibited? You can close this time wasting thread if you like. Paul.

May 30, 2014 at 6:35 PM Flag Quote & Reply

MTX371
Member
Posts: 46

Next time I will undo the 7 screws before asking... 

May 30, 2014 at 6:36 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8885

It's a pretty basic first step, Tim.


Movement and everything looks like new.

Will try to have a look at the PCB the next days.

The watch looks like from the dealer - can´t imagine that there should be a fault in the PCB.


With the state of that PCB, you can't honestly expect us to believe that there was no evidence of battery acid attack visible on the the movement back-plate.


May 31, 2014 at 1:08 AM Flag Quote & Reply

MTX371
Member
Posts: 46

It was really nothing to see... Sorry again... :roll:

I changed the PCB and now everything is ok except for the 30 minutes chronograph... Tried to poke it a little bit, but nothing happened...

Also "basic" first step or what shall I do now? Can there be a fault on the PCB that the 30 minutes chronograph doesn´t move? Shall I oil the gearwheel a little bit? If yes, how do I do that?

Thanks for your help again...


May 31, 2014 at 4:07 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8885

Well I can't say I'm exactly surprised, Tim. Look at your own first photo. The cause of your 'latest' problem was staring you in the face.




No matter how well you may have cleaned up the coil's contacts, I suspect it was wasted effort. The battery acid has probably eaten through the connecting wires. Try swapping it for a known good one. Make sure you've cleaned that switch contact post properly too.


May 31, 2014 at 4:46 PM Flag Quote & Reply

MTX371
Member
Posts: 46

So I should change the coil block?! Or the coil contact? How do you clean those contact most efficiently? With Isopropyl-Alcohol?

June 1, 2014 at 4:56 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8885

The coil windings and their contact sections are supposed to be one and the same part, Tim (Seiko p/n 4002.726 for C and D).

However I suspect when you undo the retaining screw on your 30 minute coil, the gold-plated contacts will probably fall off.

Suggest you read the manual some time. Partial illustration from the top of Page 6 clearly shows them as one part:

June 1, 2014 at 6:41 AM Flag Quote & Reply

MTX371
Member
Posts: 46

Paul. Thank you very much!!

It was the right hint! Took out the faulty coil contact. Took a one from a donor watch - destroyed the first one (the very tiny connections to the contact plate), but I was successful with the second one...

Watch is working fine 100% now...

And I am very happy!! Thanks again!

June 1, 2014 at 3:15 PM Flag Quote & Reply

ketap
Member
Posts: 28
Good work Tim :-)
June 4, 2014 at 1:10 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 8885

Perhaps you might post a photo of the repaired watch, sometime, eh, Tim ? ;)


I was thinking afterwards. This case of battery acid damage to the movement's PCB is probably one of the worst we've seen recently.

Having said that, I doubt anything will ever beat DaveS's 'toasted' 7A28-7070, which he posted on SCWF a couple of years back. :lol:




Simon (Sir Alan) and myself have encountered it quite a few times and documented it fairly comprehensively in various other threads.

Depending on (bad) luck, it can sometimes take very little in the way of battery acid corrosion on a PCB to kill a watch stone dead. :(

Here's another such recent example - again a 7A28 (RAF Gen. 1) - which at the time of writing is still unresolved AFAIK:

http://www.seiko7a38.com/apps/forums/topics/show/9476931-is-battery-terminal-damage-reason-for-dead-movement-


June 4, 2014 at 4:50 AM Flag Quote & Reply

You must login to post.